In a previous blog on dementia, I expressed positive surprise to hear that dementia is described as a “preventative” disease. What welcome news, even if I couldn’t quite reconcile this with the evidence, which suggested we can meaningfully lower the risk but not eliminate it.
More recently, neurologist Dr Dale Bredesen has gone further, to say that not only is Alzheimer’s preventable, but in some cases, it is reversible, particularly when caught early. In this article, I explore the evidence.
One point is undisputed: prevention strategies should start as early as possible. As the Chinese proverb reminds us, “The best time to plant a tree was 20 years ago. The next best time is now.”
The Perfect Storm for Dementia
We are facing a perfect storm for rising dementia cases. Whilst an ageing population plays a role, so too does our modern lifestyle: more sedentary living, ultra-processed diets, chronic stress, sleep deprivation and greater exposure to environmental toxins.
These factors drive insulin resistance, chronic inflammation, mitochondrial dysfunction and cardiovascular disease – all of which impair brain health.
Although the brain represents just 2% of body weight, it consumes 20% of our calories, cardiac output and oxygen. This disproportionate demand highlights how dependent the brain is on good blood flow and quality nutrients.
When these are compromised or when the brain’s ability to detoxify is impaired, the brain responds to defensively. Amyloid and tau, so long associated with Alzheimer’s, may represent a protective response to the injury, rather than be the primary cause of disease.
Creating a Brain-Healthy Life
Before considering the more controversial claims, there is a strong scientific consensus that brain health requires a protective lifestyle, which includes all the following seven pillars:
Exercise: the brain loves movement and resistance training. Exercise improves insulin sensitivity, mitochondrial function, blood flow and neuroplasticity. Ideally, it should be as habitual as brushing our teeth.
Nutrition: a whole-foods, vegetable-first diet with regular fasting windows supports metabolic health. Focus on non-starchy vegetables, fruits, fermented foods, nuts and seeds. Minimise sugar and refined carbohydrates. Time-restricted eating (e.g. a 10-hour window from 9 am to 7 pm) with a 3-hour gap between the last meal and sleep further supports metabolic resistance.
Sleep: Seven to eight hours of quality sleep is essential for brain detoxification. One to two hours of deep sleep is critical for clearing amyloid and tau proteins. Fragmented sleep undermines this process. Alcohol suppresses deep sleep; sleep apnea repeatedly interrupts it; and insomnia keeps the brain in a hyper-aroused state. All require active management.
Stress: Avoid chronic stress, which increases cortisol, a neurotoxin. Cortisol increases the amyloid build-up, shrinks the hippocampus and impairs memory consolidation. Practices such as meditation, yoga, breathing exercises and social connectivity help to mitigate this risk. Loneliness is a significant and often overlooked contributor.
Detoxification: remove the toxic brain threats. Beyond smoking, modern threats include microplastics (from cups and containers), mercury in some fish, mould, pesticides and air pollution. Sweating, whether through exercise or sauna use, is a good way to detoxify.
Brain Training: The brain thrives on challenge. Learning builds cognitive reserve, which protects against dementia. Mental stimulation comes from learning new skills, languages, complex movements and coordination. Activities like dancing or martial arts combine cognitive challenge with physical activity and social connections.
Supplements: some essential nutrients may need a top-up if dietary intake is insufficient. The essentials include B12, Omega-3, Vitamin D, B6, folates, magnesium, creatine, polyphenols, and probiotics. Always choose high-quality, evidence-based products.
Genetics Loads the Gun. Lifestyle Pulls the Trigger
Genetics influence the dementia risk but does not determine destiny.
The highest known genetic risk for Alzheimer’s disease is APOE4. Each person carries two APOE genes, one from each parent. For those without an APOE4 gene, the risk of Alzheimer’s by age 85 is around 9%. With one APOE4 gene, it’s 30,% and with two, it’s 60% to 70%, based on a typical Western lifestyle.
Crucially, even an elevated genetic risk is modifiable. Protective lifestyle factors can significantly reduce this risk.
Is dementia reversible?
This is where the debate becomes more controversial.
Like cardiovascular disease and cancer, dementia is multifactorial and progressive. Dr Bredesen defines four stages of cognitive decline, with the fourth being full-onset dementia. Today, dementia is typically detected at this late stage.
Dr Bredesen advocates regular testing from midlife, arguing that early-stage cognitive decline offers the greatest opportunity for reversal. He compares this to cancer, where it is detected as early as possible, rather than waiting for the disease to reach an advanced stage.
He argues that when brain health threats are removed early, the brain can regenerate, as this early damage is not structural. In some cases, the cause may be specific and treatable, such as toxin exposure, sleep apnea, or vitamin B12 deficiency.
To support this position, Dr Bredesen cites case studies where he has slowed decline or improved brain function, even in some individuals with more advanced impairments. However, today a randomised control trial has not yet been completed to test his theory, but one is expected to report within the next few years.
Mainstream medical consensus remains cautious and considers that nothing can be done to reverse dementia with existing drugs. As a result, early detection has minimal benefits and could instead increase anxiety.
This position may reflect the fact that dementia is usually detected late, often following ten to twenty years of silent pathology, by which stage the structural damage may be permanent. Earlier in the disease process, when neurons are alive but underperforming, there may be greater potential for functional recovery.
What all experts broadly agree on is:
The dementia risks are modifiable decades before the onset of symptoms
Lifestyle and environment can meaningfully reduce the risks
Once dementia is full-blown, reversal is not possible with the current science.
In Summary
Dementia has multiple causes and is progressive, but even with a genetic disposition, it is not inevitable. Damage to brain health reflects the cumulative effects of a poor lifestyle and environment over 20+ years. A protective lifestyle, following the seven pillars above, could significantly reduce this risk.
Today, dementia is detected too late. Early detection could help, as some causes are treatable, or the damage is not yet structural. However, to determine whether dementia is reversible, we need to await the results of a rigorous randomised controlled trial.
For now, we should focus on what is uncontroversial and within our control: building a protective lifestyle, starting tomorrow.
